The invention relates to cohesive bulky continuous filament yarn and its production, and is more particularly concerned with improved yarn for use as pile in pile fabrics, especially cut-pile carpets.
When carpet yarn is used in cut-pile carpet constructions known as shag and saxony, wherein each tuft must appear as a coherent yarn without excessive splaying of tuft ends in use, a single bulked yarn of continuous thermoplastic filaments has been twisted, wound on skeins, tumbled to develop crimp, heat-set in a steam autoclave and rewound from skeins to cones before being tufted into fabric to form the carpet. The process of twisting and heat-setting twist in the yarn is costly and reduces the bulk of the yarn. High twist is used to provide tufts having adequate coherency plus a lustrous twisted appearance due to substantial helical parallelism of the surface fibers. Such yarn has considerable torque and must be processed at high tension to avoid kinks which would obstruct delivery tubes and needles of tufting machines. Processing difficulties would, in turn, result in nonuniform tuft appearance. Without such twisting and heat setting the cut tuft ends expand until they tangle with neighboring ends, giving a high bulk but a matted appearance wherein individual tufts are indistinguishable.
Bulked yarns of highly entangled filaments have been prepared which have adequate coherency without twisting, to prevent excessive splaying of tuft ends, but such yarns have had a random crimped configuration in surface filaments which do not provide the appearance desired in shag or saxony rugs and have had protruding filament loops which make processing difficult.